Anyone know the differnce C.A.R., XM177, EM4?

[PandaBearBG]

I currently have a a 20" heavy AR, large scope, bipod, all that good stuff for that long range shooting. However I am going to get a 16" upper with its own dedicated BCG, well just because. I don't really care about brands or different calibers (sticking with 5.56) and I don't care about M4 feedramp cuts or military specs or history, since I will be buying civilian versions. I am just curious abou the different designs. Does anyone know the difference between the following?

1: C.A.R
2: XM177
3: EM-4

Is it that the XM-177 just have the long 5 1/2" flash suppressor integraged into the barrel? Are the CAR's just straight barrels? Are EM-4's the only ones with 203 cuts in the barrel? Are the only differences basicly barrel shape?

I know there is a chronocologial military history about how these variants grew and improved from each other. But now a days they are basicly civilian version and the only difference I can see is the barrel design and the longer permanent flash suppressor on the XM-177.

Sorry for being so blunt, but AR questions can get pretty indepth and debatable, I just wanted to see if the THR community knows the basic differences between the civilian copies.

Thanks!

 

[dfariswheel]

The CAR and XM177 are "sort of" the same thing.
Each current maker uses the names for slightly different rifles.
During the Vietnam War the XM177 was called the CAR by users even though most were made by Colt and were clearly stamped "Colt Commando".

"In general", a current commercial (again depending on the maker) CAR will have a 16" barrel and collapsing stock.
An XM177 will have a 10" barrel with a permanently attached 5 1/2" muzzle attachment.

The M4 is rather different.
It has the M4 barrel with the groove in the middle to allow attaching a grenade launcher, and a carrying handle that is removable to allow attaching some type of optical sight.

A great deal depends on what terms the maker uses, but the M4 is usually pretty much the same across the industry.

 

[PandaBearBG]

Thanks dfariswheel! That clears alot up, also are bushmasters the only company that uses the larger pins? The locking pins that connect the uppers and lowers? They have the larger pins instead of the standard ones, correct? So they would not be compatible with my standard lower?

 

[rocky branch]

I carried a CAR in VN, 68-70.

Mone had a long supressor and I have seen shorter ones.
Very handy in thick bush.

The muzzle blast on both was significant.
I don't think the were stamped "Commando," but could have been,

 

[Acera]

PandaBearBG some pin stuff depends on the maker. Colt was the original large/small pin maker, and some of the older Colts are large pin guns. Rumor has it if they did not drill the small hole exactly right, they had to drill it bigger to get it centered, and thus made it a large pin gun. Don't know how true that is, and I am sure someone on here will correct me it that is wrong. I did not know any manufacturer made large pin lowers anymore. Parts are still easy to find for them, though.

The front pivot pin is interesting also. They used to use a .312 sized hole, and now the .250 is considered standard. The larger hole had a special pin that allowed the user to snug up the fit between the upper and the lower, it was removable. The newer system had a captured pivot pin, that does not come out (at least not easily). From what I know, the back pin has always been the same. They make special pins if you have an old large pin lower and want to get a new small pin upper. Here is one on Midway.

http://www.midwayusa.com/viewProduct/?productNumber=316328